Future driver assistance systems utilize increasing amounts of surroundings information via radar, ultrasound, cameras, etc., thus enabling a plurality of possible driver assistance functions that assist the driver in critical driving situations, either to protect the driver and/or vehicle occupants or to prevent other traffic participants from being harmed.
Customer acceptance of such driver assistance system stands or falls by the actuators available in the vehicle, which initiate various vehicle reactions in accordance with the current vehicle state or driving situation, for example automatic emergency braking to avoid a rear-end accident or to avoid a collision with a pedestrian.
Interventions in the current operating state of a vehicle can occur in many ways. The possibility exists, for example, of applying control to various elements of the chassis, the drive train, the steering system, or the brakes by way of a control unit. For collision avoidance, a further distinction can be made between interventions that reduce the speed of the vehicle and interventions that also additionally modify the direction of travel.
Especially with braking interventions, the potential of an intervention depends critically on the available pressure buildup dynamics, and, for convenience-oriented functions, additionally on the resulting noise of the actuators used (as should be known, for example, from a conventional ESP/ABS system).
In particular, pressure buildups by way of the piston pump of an ESP hydraulic system offer insufficient pressure buildup gradients, and moreover generate considerable noise as a result of hydraulic and mechanical coupling to the vehicle.
The document DE 2012 104 793 A1 discloses a collision avoidance system that furnishes automatic steering control using differential braking in the event that standard steering control of a so-called “main vehicle” fails. The system ascertains whether a collision with an object, for example another vehicle or even a person, is imminent; and if so, ascertains an optimum path for the main vehicle to travel along in order to avoid the object in the case of an otherwise possible collision. The collision avoidance system can ascertain that automatic steering is necessary in order to cause the vehicle to follow the optimum path for avoiding the (collision) target. If the collision avoidance system ascertains that automatic steering is necessary, and ascertains that normal vehicle steering has failed, the system uses differential braking to steer the vehicle along the path.